To roam means to walk or travel freely without a particular destination in mind.
When people say they'll be out roaming around this weekend, it usually means they won't have any specific plans and will just see where their day takes them. They might drive to the countryside, visit some parks, or go for long walks just because they feel like it. Sometimes we talk about animals roaming freely in a field or forest, which is also what's happening – no particular direction or purpose, just exploring and enjoying themselves.
To wander or travel freely and with no specific destination.
